Food products that comprise more than one product layer are well known in the art. It is also known that, if the food product comprises layers, wherein at least one of the layers contains water so that the layers have a different water activity (Aw), these products often suffer from migration of the water from one layer to the other layer. Very often this migration has a negative impact on the performance of the food product, e.g. the product might suffer from sogginess, resulting in a product with insufficient appearance or texture. Therefore in these products a water barrier layer is very often used in order to decrease and if possible to avoid the water migration. A good water barrier layer should thereby fulfil the following criteria:
it should have a low water permeability.
it should stick well to the surfaces of the layers that it is supposed to protect against the water migration.
it should not be too brittle, so that the formation of cracks in this layer is avoided as much as possible.
it should have an appropriate viscosity at the temperature it is applied during the making of the food products, or else the processing becomes far too difficult.
the mechanical properties should be alright so that the layer can survive handling procedures, such as packaging without breaking.
the layer should not be noticeable during eating, otherwise the eating quality is affected in a negative sense.
the layer should not be apparent to the consumer.
So far most of the barrier layers present in commercial products are based on acetoglycerides. However these layers still have a considerable water permeability and are not always flexible enough and thus do not have the desired mechanical properties.
From U.S. Pat. No. 5,130,151 it is known that compositions useful as moisture barrier for a food product can consist of edible oleaginous material with a melting point above ambient temperature and a portion of a material selected from sucro poly fatty esters and sugar alcohol polyol polyesters and a wax. The waxes mentioned do not include sunflower wax, while according to this document always a polyester must be present in the composition.
In our earlier patent application EP 910 955 (published April 1999) we disclose blends of wax esters and triglycerides as fat replacer. The wax esters consist of at least two different wax esters from which at least one has a melting point of 20 to 60xc2x0 C., while the mix of wax esters has a melting point of 15 to 45xc2x0 C. The triglycerides that can be present can be selected from the group of: liquid oils, fractions of hardened liquid oils, hardened liquid oils, cocoa butter, cocoa butter equivalents, palm oil, fractions thereof, fish oil, fish oil fractions, hardened fish oil or fractions thereof, enzymically made equivalents of above fats and mixtures of one or more of these fats. In example 2 of this document a wax is prepared from behenyl alcohol and the fatty acids of sunflower oil. However this product has a composition that is different from sunflower wax.
We performed a study to find out whether we could find new compositions that could be used as water barrier layers in food products without the problems indicated above.
This study resulted in the finding of novel blends of edible organic materials, comprising a natural wax and glyceride materials, wherein the natural wax is a wax derived from sunflower oil and the glycerides substantially are triglycerides with a solid fat content at 20xc2x0 C. (N20) as measured by unstabilised NMR techniques, of at least 20, preferably at least 40, most preferably 50-95 and wherein the wax is present in the blend in an amount of 1-80 wt %, preferably 2.5-60 wt %, most preferably 5-40 wt %. The N-value mentioned here is measured by NMR techniques on a fat that has not been stabilised i.e. the fat has been subjected to the following pretreatment:
melting at 80xc2x0 C.,
cool it to 0xc2x0 C. and
hold at 0xc2x0 C. for 60 minutes,
then heat to measurement temperature (here 20xc2x0 C.) and hold at 20xc2x0 C. for 30 min before measuring the N-value.
Preferred blends are blends of
1. a wax of sunflower oil, obtained by cooling of sunflower oil to 0-20xc2x0 C., holding the cooled oil for 12-48 hours, removal of the wax by filtration and refiltration of the wax at 30-70xc2x0 C. and
2. other glyceride components.
Most preferred blends are blends wherein the wax is obtained after a further purification process involving at least one of the following procedures:
1. melting, cooling to 50-70xc2x0 C. and filtration or
2. dissolution in a solvent, such as acetone or hexane, cooling to 20-60xc2x0 C. and filtration, recovering the wax as a solid.
The glyceride component present in these blends can be selected from a wide range of fats and oils. Preferably the glyceride component is selected from the group consisting of: liquid oils, partially or fully hardened liquid oils, fractions thereof, palm oil, or fractions thereof, shea oil or fractions thereof, cocoa butter or fractions thereof, sal or fractions thereof and mixtures of these oils.
The wax component in our blends often is obtained as a mixture with an oil from which it is isolated, as the triglycerides are often difficult to be removed completely. We prefer to use blends wherein the glyceride component at least partially is a liquid oil component as present in the sunflower wax as obtained by the process set out above.
In many instances it is preferred to add a filler material to the barrier layer, eg to decrease its caloric content or to improve the textural or other properties of the layer. Therefore we prefer to use blends of organic materials and a filler material wherein the blend comprises 90-10 wt % of a filler material and 10-90 wt % of the blend according to the invention. Typically the filler material is selected from the group consisting of
1. carbohydrates, in particular sugars,
2. thickeners, in particular cellulose powders or fibres, starches and modified starches,
3. emulsifiers, in particular mono- and diglycerides and lecithins,
4. powders, in particular dairy powders selected from butter milk powder, milk powder and skimmed milk powder and cocoa powder.
Part of the invention are also food products in particular multi-layered or compounded food products comprising at least one barrier layer, separating two layers with different water activity and wherein the barrier layer comprises a blend with the composition according to the invention.
These food products beneficially comprise at least three phases A, B and C,
A being a baked flour based system
B being the barrier layer according to the invention
C being a water based food composition and wherein the layers A and C have a water activity Aw such that the difference {(AW)Axe2x88x92(Aw)c}abs hereof is at least 0.1, preferably at least 0.3.
Herein layer C preferably is selected from the group consisting of fat emulsions (water or fat continuous), creams, custards, jellies, ice cream, sauces, fruit, vegetables and jam.
In another type of food product the migration might take place via the air surrounding a mixture of small entities of the components of the food product. Examples hereof are blends of dried fruit and a cereal, such as corn flake or wheat flakes, which blend is provided with a barrier layer, wherein the barrier layer comprises a blend according to the invention.
A last embodiment of the invention is the use of a blend of edible organic materials as a barrier layer in food products wherein a barrier layer comprising the blend according to the invention is applied to prevent moisture migration in the food product and to improve the texture of the food products according to the invention.